I have a correspondent who has brought up that old argument about evolution violating the 2nd Law. I am sorry to say that when I was young and uneducated, I knew just enough about entropy that the argument sounded plausible and science-y.

But here's what I think these days, with Wikipedia citations embedded.

Entropy is a measurement of a system's disorder, and can often be treated as a loss of information. I assume that you will agree, however, that living things on Earth are highly organized and contain much information, at least when compared with naturally-occurring inanimate objects? That is, the fact that life exists and is seemingly complex seems to violate the 2nd Law, which is an expression of entropy? At the very least, we certainly require some explanation for life's complexity!

Please notice that I have said nothing so far about evolution. It is not evolution itself that seems to violates the 2nd Law, it is merely that fact that life is complex and enduring.

Many people often assume that evolution especially violates the 2nd Law, because they assume that evolution's most likely result is greater complexity. This assumption turns out not to be correct. Evolution itself is simply populations changing over time. Sometimes the result might be more complex, some time less so. So, again, there is nothing that specifically ties evolution to a violation of the 2nd Law. This is just an assumption in the creationist literature that has not been critically examined.

So, since evolution itself doesn't necessarily contradict the 2nd Law, what does? Again, it is simply the apparent complexity of living things, diversifying over time and seemingly able to resist the universal tendency to disorder. It is the very fact of life's properties that seem to violate this law, and while evolution is naturally advanced by scientists as a explanation for life's properties, it is not evolution itself that appears to violate the law.

In fact, since mutations are 'errors' or 'mistakes', they can be thought of as a means by which information is lost. This isn't always the case, but there can be no denying that gene sequences are not perfectly copied, and that information is lost, entirely in keeping with the 2nd Law. Evolutionary biologists will tell you, however, that these mutations form part of the pool of variation on which Darwin's principle of natural selection is able to act. In that sense, evolution not only does not violate the 2nd Law, it is in a sense dependent upon it.

The question then becomes what is the source of the original order. Interestingly enough, the 2nd Law says nothing about that. Christians naturally assume that the source of the Universe's original order is the Creator, but it is important to remember that we Christians only 'know' this by faith, and that the 2nd Law is not really a theological construct that points to any faith, much less Christianity. It is simply a generalization that systems tend to disorder, and in particular that the universe is becoming less ordered all the time. Properly speaking, the 2nd Law is not a law about the Earth, or our solar system, but about the Universe as a whole.

What, then, is the source of the local tendency for living things to diversify and become more complex? The answer is simple: a surplus of free energy, most of it provided by the sun, which on the average bathes every acre in North America with about 4 megawatts of energy per hour. This is far more energy than living things can actually use, but even at 100:1 exchange rate, we are talking 40 kilowatts per hour per acre. This is more than enough energy to drive what Schrodinger called the 'negentropy', the situation of apparently-decreasing entropy.

This decrease, of course, is an illusion. Things here on Earth still fall apart, and in order to provide us with surplus energy, the Sun is busy fusing hydrogen to form helium. At some point billions of years in the future, the Sun will run out of hydrogen and other light atoms to 'burn' as fuel. At that point, the 'party' on Earth will be over, and, in fact, the solar system will largely cease to exist. So, as the saying goes, someone has to pay for that party eventually. But it is the Universe as a whole that gets the bill, not just the inhabitants of our local system. Remember: the 2nd Law is properly speaking about the Universe as a whole. A local system can experience a temporary decrease in entropy due to the availability of surplus free energy, but in the long run the total entropy of the system must increase.

Since life is flourishing here in that window of time in which there is a surplus of free energy from the sun, how life diversifies and changes over time does not violate the 2nd Law.